Academy of Science: how has climate changed during the recent past?
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This is an extract from The Science of Climate Change — Questions and Answers, published by the Australian Academy of Science and distributed to members of parliament, every local government authority in Australia and every Australian high school, in August 2010. Crikey will be running a series of extracts, including canvassing common myths. Global average temperatures have increased over the past century Measurements from many hundreds of thermometers around the globe, on land and over the ocean, show that the average near-surface air temperature increased over the 100 years to 2009 by more than 0.7°C. Many of these instrumental records, which began in the second half of the 19th century, were not initially designed to be used for climate monitoring. This means they have to be carefully analysed to deal with changes in instruments, observational practice, location, and the growth of cities (see Box 3).
After accounting for these issues, temperature increases are largest in the continental interiors of Asia and north Africa, regions which are distant from major population growth areas (see Figure 3.1 and Figure 3.2).
The rates of observed near-surface warming increased in the mid-1970s. Since then, the global land surface has warmed at about double the rate of the ocean surface. Measured warming over the past 50 years was nearly twice the rate of that for the past 100 years. The last decade has been the warmest yet recorded (see Box 4).
The overall warming has led to an increase in the number of record high temperatures, and decrease in frost frequency and the number of record low temperatures over the past century (see Figure 3.3).
Over the past three decades, satellite observations of temperature at the Earth’s surface and in the lower atmosphere have also shown warming (see Box 5). In contrast to the surface warming, the atmosphere above about 15 km elevation (the stratosphere) has This provides one clue that the observed warming is due to human activities.
The upper 700 metres of the ocean is storing about 90% of the additional heat absorbed by the Earth’s whole climate system since 1961. The surface ocean has warmed by 0.5°C from the 1970s to the early 2000s. Averaged over the upper 700 metres of the ocean, the average warming is much smaller, only about 0.1°C, but very important because of the large amount of stored heat this represents. Temperature observations are not the only evidence of recent climate change
Australia’s climate has changed along with the global climate In Australia, the average surface temperature has increased by about 0.7°C since 1960, with some areas having warmed faster and some showing relatively little warming (see Figure 3.5). The warming has caused an Australia wide average increase in the frequency of extremely hot days and a decrease in the frequency of cold days (see Figure 3.3).
While the longer term trends in rainfall are less marked, there have been significant increases over north-western Australia, and decreases over south-western and south-eastern Australia since 1960 (see Figure 3.6). The warming and decreased rainfall over south-east Australia
It is likely that these trends are related to shifts in pressure patterns over southern Australia, particularly the intensification of the subtropical high pressure belt. Regional ocean currents have also changed. For example there has been a southward shift of the Antarctic Circumpolar Current and an increasing southward penetration of the East Australian Current, associated with wind changes in the South Pacific. Sea level has risen around Australia at a rate of about 1.2 millimetres per year since 1920, resulting in coastal inundation events becoming more frequent. Since the establishment of the Australian Baseline Sea-level Monitoring Project in the early 1990s, sea level measured relative to the land has risen at about 2 millimetres per year in the south east, and over 8 millimetres per year in the north west. The Australian Academy of Science, which represents Australia’s foremost scientists, provides scientific advice to policy makers and promotes excellence in Australian science, has devoted considerable resources to untangling the science of climate change and presenting it in a simple and easily understood format. The full report can be downloaded here for free. |
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42 Comments
Just a question — don’t bite my head off — could some of this be caused by deforestation and aridification acting on the climate through surface changes to albedo and water cycles, independently of the greenhouse-gas mechanism?
@ FreeCountry
Yes and volcanic activity and methane from cattle / beasts.
@ Freecycle, Deforestation and aridification also release CO2 equivalent (burning and rotting vegetation and increases in livestock on the resulting land). As deserts and clear land have higher albedo than forests, albedo change would actually be a cooling influence (hence Stephen Chu’s suggestion that we should paint all roofs white ). This is one of the reasons melting arctic ice is a concern; as the ice melts the albedo drops leading to the ocean absorbing more heat in a vicious cycle.
There are some changes in the water cycle due to the dramatic increase in irrigation across the world leading to higher evaporation rates, but the effect on temperature is an order of magnitude or two lower than that caused by CO2.
Indeed, freecountry, something that strikes me looking at the 1960-2009 rainfall anomaly map is how many of the greatest rainfall declines are concentrated around areas where urbanisation has replaced vegetation. I wonder if there are some local effects going on there (aerosol or particulate pollution and/or drop in transpiration, as well as albedo change), superimposed on the more regional and global trends.
Deforestation does have a definite impact on local climate, which exacerbates the climate change problem where it occurs.
On the other hand, there is the potential to quickly reverse warming on a local scale through innovative solutions that address this phenomenon, like this one:
http://arstechnica.com/science/news/2011/03/switching-biofuels-could-do-a-double-whammy-on-climate-change.ars
However, this is all independent of the global impact of climate change. Most of the energy introduced into the climate system is trapped in oceans, and there isn’t much we can do to reduce that problem by using mechanisms that address the issue on a local scale. Also, many of the places experiencing the largest warming are well away from any population centres.
The struggle to halt the global warming trend will be helped by local solutions (which have global benefits anyway), but it will also require a real effort to transition to a low-carbon economy. In the end, all the models show that the root cause of climate change is greenhouse gases, so they should be the primary target of any efforts.
I won’t pretend to know any more than either freecountry or mark duffit, but I think as simple logical answer would be that rainfall maps always reflect settlement, as people like living near fresh water.
To my eyes, that map looks like the tropical zones got wetter, and the temperate zones got drier. Why the desert got wetter I don’t know.
The surface temperature map (which I would have thought albedo related to more directly) does not appear to involve a urban distribution at all.
I’ll quote two paras from above:
“The upper 700 metres of the ocean is storing about 90% of the additional heat absorbed by the Earth’s whole climate system since 1961. The surface ocean has warmed by 0.5°C from the 1970s to the early 2000s.
Averaged over the upper 700 metres of the ocean, the average warming is much smaller, only about 0.1°C, but very important because of the large amount of stored heat this represents.”
Please tell be there’s an editing error here…. or is it true what they said about me and my pedantry?
This is how our “foremost scientists” deceive us.
For instance, they imply more dramatic changes in climate over the past 50 years. This is a shameful abuse of logic. As the 100 year trend maps indicate, there has been little change over a century.
The reason the 50 year interval is chosen, is because the 60s and 70s experienced record high rainfall and below avg temps. So a decadal trend since 1960 will exagerate the return to an early 20th century climate.
it’s simple logic, not catastrophic climate change.
@Charlie, I’m not quite seeing your issue. Admittedly the flow would be better if the first sentence were placed last, thus:
“The surface ocean has warmed by 0.5°C from the 1970s to the early 2000s. Averaged over the upper 700 metres of the ocean, the average warming is much smaller, only about 0.1°C, but nevertheless this is very important because of the large amount of stored heat this represents. The upper 700 metres of the ocean is storing about 90% of the additional heat absorbed by the Earth’s whole climate system since 1961.”
Any better?
I’m glad the Australian Academy of Sciences admits that a linear trend of a decade is a relevant analysis to examine the magnitude of warming.
It’s a pity they get the recent 10 year trend wrong as there was cooling from 2001-2010, using the IPCC global dataset Hadcrut.
http://www.woodfortrees.org/plot/hadcrut3gl/from:2001/to:2011/plot/hadcrut3gl/from:2001/to:2011/trend
Since 1998 the warming trend is 0.01C.
That’s not exactly accelerated warming.
http://www.woodfortrees.org/plot/hadcrut3gl/from:1998/to:2012/plot/hadcrut3gl/from:1998/to:2012/trend
Funny how the don’t mention sea surface temperature since 2000.
That’s because global SST has cooled since 2001.
http://www.woodfortrees.org/plot/hadsst2gl/from:2001/to:2012/plot/hadsst2gl/from:2001/to:2012/trend
This is a poor Crikey effort at pushing AGW science to support the disastrous carbon tax.
I particularly liked the statement “Measured warming over the past 50 years was nearly twice the rate of that for the past 100 years.”
Yet another calculated deception by our best scientists and the IPCC.
If you listened to them you wouldn’t know the earth had cooling cycles in the 20th century.
Phill Jones of CRU fame admited the reality of warming rates to the BBC: “As for the two periods 1910-40 and 1975-1998 the warming rates are not statistically significantly different.”
Mark etc, what is the difference between “surface ocean” and the “upper 700 metres of the ocean”, and is the implication here that the depths, the average thousands of metres of water profile across all the oceans deeper than 700m, are not storing any of the additional heat absorbed by the Earth’s whole climate system since 1961”? Doesn’t sound right, but I don’t know what’s wrong with it.
TONES9, could you draw up that “decadal trend since 1960”, because your words don’t make sense.
The reason I ask about devegetation and albedo change is because if those mechanisms operate from the surface, in parallel to (while also contributing to) the atmospheric greenhouse, then they would be having an overweight effect on climate, in excess of that which their CO2 emissions would suggest.
And if that’s true, then the soil sequestration strategies suggested in articles such as this one (( theaustralian.com.au/news/features/what-happens-when-the-food-runs-out/story-e6frg6z6-1226004670563 )) might have a bigger effect on climate mitigation than the quantity of carbon sequestration might suggest. In addition, that is, to having net positive effects on GDP and reducing world poverty.
@Charlie, the ‘ocean surface’ is, these days, what can be sensed remotely from satellites via thermal infrared radiation. This corresponds to only the top few millimetres.
With ocean circulation taking place over the order of hundreds to thousands of years, there hasn’t yet been enough time for significant heating of the ocean deeper than 700 m.
The world is getting warmer. Something is causing this to happen, and the most plausible explanation so far is the increase of carbon dioxide in the air. In the scheme of things, oil will eventually run out, and moving toward alternative energy before it runs out is a good move, because the alternative energy infrastructures need at least 50 years to put in place. By the time oil start to go up in price drastically, it will already be too late.
OK, so you think that the ‘ocean surface’ is a few millimetres in depth and according to the text this thin sliver has increased in temp by 0.5°C from the 1970s to the early 2000s. On its own this is probably not a very important statistic but when it is used in that part of the article which was addressing the storage and distribution of the increased warming (ie in the top 700m of ocean) it is actually an irrelevant statistic. Effectively, nothing is being stored in the top few millimetres of ocean that isn’t dwarfed by that stored in 700m. Think about the amount of expansion that occurs in the top few millimetres. It would be microns worth of sea level change.
So I suppose my “issue” is the mixing of two separate concepts in the one train of thought and the loss of meaning for both of them in the process.
Hugh it’s quite simple really.
Wish I could draw a graph for you.
And no point in posting a link cos these moderators hold it up for hours.
Still waiting for my 5.08pm post showing global cooling in temp and sea surface temp this decade.
I see Hugh’s point, it is a bit odd. If the delta T at the surface is so much steeper over time than the delta T lower down, what does that imply … that the convection coefficient of seawater has changed? That climate change is happening faster than water molecules can circulate through 700m depth? That they’ve started taking surface readings in the middle of the day instead of the middle of the night?
No matter what we do, we are not going to change climate change in our, or childrens life time, so it would be more effective to make changes to adapt to what is definately coming, instead of wasting time playing politics.
So ToneS9, can you explain figure 3.3 if we’re not seeing dramatic and accelerating climate change? Or do you think that the Bureau have been carefully faking data for the last century so they can win support for a carbon tax?
Strewth I am sick of it all. After witnessing the polls today where the Labor preference has dropped to 39% , because of the proposed carbon tax, I’ve concluded that 61% of the Australian public are donkeys (what an insult they are to our 4 legged friends.)
Such stupidity, such illiteracy, such ignorance and wanton greed belongs in the tenth century.
The donkeys have a lower IQ than the Easter Islanders. At least their ignorance could have been sustained considering the massive human footprint and wholesale ecocide commenced after occupation around a.d. 900.
Oh God now that idiot from the IPA is on the tellie - ” hee haw hee haw” says the donkey. Where’s the alka saltzer?
Stephen, dramatic and accelerating global warming would be global.
So a cooling decade doesn’t fit the alarming description.
Fifty years of Australian data is not relevant to causal attribution.
Flower, ALP first preference is a pathetic 30%.
It’s a shame you have such extreme intolerance of your fellow humans.
I’m sure you thought Australian’s were smart when a majority supported a tax.
It is.
It does not show what you think it does.
Yes it is. You can’t dismiss it because you don’t like it.
4.5 billion years of climate change versus the last 200 years of human industrialisation? Let me do the math here and say the climate has always changed and us puny humans have had nothing to do with it what so ever! It wasn’t that long ago scientists were telling us we were about to have another Ice Age, Governments here in Australia as recently as 3 years ago said we might not see rain again in some parts. Mother nature must be rolling around on the floor at all of us knowing that one day she will swat us like a fly when she’s good and ready!
@Hugh and FC, I think you’ve got the wrong end of the stick. It’s not that there’s a sharp thermal boundary between the top few mm (i.e. sea surface temperatures) and the rest of the upper 700 m of ocean. The distinction is primarily an artifact of our measuring tools, coupled with the fact that it’s the former (SSTs) that are of direct importance in driving atmospheric systems (witness ENSO).
That’s essentially it, though I’d say ‘heat can be transported’ rather than ‘water molecules can circulate’. Remember warmer water is less dense, and oceanic temperatures almost always fall with depth, so that tends to mitigate against vertical mixing.
Rich, it’s not a matter of what I think, it’s what the figures are.
@tones9 Sounds like you’ve been drinking the cool aid. So you’d say a clear upwardly trending sawtooth graph is not actually trending upward because it has little bits of downward trends in it? Have a look at http://www.youtube.com/watch?v=khikoh3sJg8
Flower - You equate a vote for Labor with a vote for the climate. What if someone like me believes in acting to reverse our damage, but also believes the Labor plan is nothing but ineffective and expensive window-dressing? I can’t even get anyone interested in the question of whether soil reconditioning with sequestered carbon could produce a climate-repair double dividend. In spite of CSIRO, the NFF, ABARE, Tim Flannery’s Wentworth Group, and every other research body interested in agriculture and climate change saying it’s the way to solve three major problems in one hit.
@freecountry
You’ve raised an interesting question. To paraphrase: “does deforestation/aridisation contribute significantly to global warming?”
I don’t think so. It would contribute to regional climate change though.
The immediate consequence of deforestation/aridisation is that the air would carry less water over these areas due to reduced transpiration. As a consequence, the opacity of the atmosphere to IR radiation would reduce , so the upper troposphere cooling should not be expected to happen.
The reduced cloud albedo would be expected to cause an increase in regional near surface warming though.
If the deforestation/aridisation was the cause of the global forcing, I expect figure 3.2 would display very strong positive temperature anomalies over south america (as opposed to a moderate anomaly) , and no positive temperature anomaly over the arctic or antarctic peninsula. The aridity of central australia has probably stayed constant too.
If you look at figure 1 at http://climateprogress.org/2009/10/10/skeptical-science-global-warming-not-cooling-is-still-happening-ocean-heat-content/
you see that the vast majority of thermal energy is gathering in the ocean. If deforestation/aridisation/urban heat effect were responsible for the warming of the oceans, they would need much higher anomalies compared to the ocean, as land has a very low heat capacity compared to the ocean.
@Johnfromplanetearth
Sure the climate has always changed. That doesn’t mean that the recent warming has the same cause as warming in the distant past.
Simple logic.
If you think it has the same cause, please tell us all what is causing the global forcing?
Funny how Tones9 suddenly loves the Hadcrut dataset, when it is compiled by Phil Jones who he hates. Couldn’t be because the other three global datasets (which include the arctic, which Hadcrut excludes) all show global warming over the last decade, could it?
Freecountry, all I can suggest is you vote Green with preferences to Liberal and join a group like Lawyers for Forests or Doctors for Forests.
Hugh, there’s only one or two papers on heating below 700 metres because it’s difficult to measure. Skeptical Science has a rundown on them.
Thank you Drail.
Freecountry: Have a look at the post in my comment above. Albedo and changes to the water cycle (due to vegetation loss) do have a dramatic impact on local rainfall and warming. Planting grasses will have a direct impact on the local climate within a short period of time, as well as making a small contribution to the climate globally. That should definitely be part of our arsenal when developing strategies to address climate change.
Nameinuse, I’m saying a ten year trend is a ten year trend. Tha Australian Academy of Sciences says “The decadal temperature trends over recent 10-year intervals remain positive.” It is wrong.
Your scary Frankenstein video is about variability in the 20th century, and 21st cent projections, which are irrelevant as to whether or not the past decade cooled.
The BoM wrote “Because of the year-to-year variations in globally-averaged annual mean temperatures, about ten years are required for an underlying trend to emerge from the “noise” of those year-toyear fluctuations.”
Jamesh, Hadcrut is used by the IPCC which provides the minimum projection of 0.2c /decade. It is the valid dataset to make comparisons. The other 3 datasets are also nowhere near o.2c/dec.
Thanks, AJH, I missed it the first time around because the link held up moderation. I’ve seen a lot of the literature (and the investment sales pitches) on biofuels, and maybe the most interesting long-term possibility is marine biofuel algae. On land there’s an unfortunate trade-off between biofuel and food production, and biofuel subsidies have even been blamed for further deforestation in Europe.
World food supply is the other great looming crisis of our time, and there are reports of global soil fertility loss in recent decades — depletion of plant roots to stabilize topsoil and the compost and bacteria mass which enable high soil yields without synthetic fertilizer — not only in Australia but much of Africa and elsewhere. When populations suffer local food shortages and aren’t industrialized enough to trade something for grains, or when global grain prices strain their purchasing powers, expensive setbacks occur, up to and including war.
Surely this is a good argument to prioritize yield-enhancing soil carbon sequestration strategies ahead of any other mitigation measures at similar or higher cost. It seems to me there’s a bit of tunnel vision about eliminating the use of coal before looking to any other forms of mitigation. But there are billions of people out there who need that carbon, so why wouldn’t we want to transfer it from sky to soil as the first order of priority. A win for the climate, a win for the world’s poor, and a win for GDP; rather than constantly looking for ways to afford expensive trade-offs.
Ah, FC. Still trying to find a more morally acceptable place to invest your coal dollars I see. Good on you.
Well yeah, there’s always the feeling that if it doesn’t hurt it won’t do any good. But hurt hits the people at the bottom of the food chain a lot more than us in the lucky country who (in a cargo-cult trading sense) can always eat things like tourism and fibre optic cables.
FC how will you implement your carbon sequestration proposal without incurring the wrath of the donkeys? Who would pay for the yet unproven technology of your project more particularly who will pay for carbon sequestration in perpetuity?
The idea is to reduce CO2 not bury it, not create it. And why would the donkeys warm to your idea of paying for the proposal when they are flat out sabotaging a carbon tax, where they remain too obtuse to grasp the fact that phasing out fossil fuel emissions will make them richer.
I haven’t yet read the links you have provided but I think we’ve already done enough geo-engineering of an outraged planet to threaten human survival.
If polluters refuse to install baghouses, electrostatic precipitators and scrubbers to capture organic and inorganic hazardous air pollutants that kill, through the current regulatory process of persuasion (and corruption), who do the pawns think are paying for the rampant contamination of the biosphere? Right – that would be the pawns of industry’s harlots for hire, who dupe the pawns into believing that a carbon tax is a great big commie plot.
It is an irrefutable documented fact, to which the pawns are oblivious, that *they* are already paying big time for the polluters’ pollution.
One signal of climate change is the devastating impacts on WA’s South West, in virtual drought for thirty years where the Swan, Frankland, Carbunup, Harvey, Collie and Murray rivers and the Thomson and Gingin brooks registered an all time record in lowest flows ever, last year. The Swan recorded 24 gigalitres, against an average of 303 GL. The Murray recorded 43.8 GL, well down on its average of 220 GL, and the Frankland 19.5 GL, compared with an average of 155 GL. So suck it up polluters - you might run out of free water for your foul operations.
Who will pay the price for permitting the nation’s most heinous polluter, WA (incompetently managed by a climate sceptic on rampage) to increase its CO2 emissions by 75% in just “a few years” according to the impotent EPA?
Oh that will be the industry’s pawns - the dumb donkeys who feast from the same poisoned tree as the whining tyrannical polluters who are looting the nation with impunity and free of charge. That will be the ill-informed miserable donkeys and avaricious polluters who would steal dunny paper from a public rest room.
Industry’s pawns will offer you two chances for carbon soil sequestration Free Country – Buckleys and none. It’s time to walk like an Egyptian.
FC: ..not to mention eating the tourists (but, please, only if you are a crocodilian Australian, crashed in the Andes, or possibly of the Fore tribe).
Flower:
Actually, R&D in soil carbon sequestration is going like the clappers, with Australia at the forefront, largely because we’ve lost so much topsoil in the last century. What’s dragging the chain is cost-effective technologies for measuring it. It requires a big taxpayer investment, with results to be measured step by step before making the next instalment. The payoff would be that carbon-rich soils grow more yield without giving up their carbon mass.
Please see this link (( carboncoalitionoz.blogspot.com/2011/02/global-summit-woodstock-of-soil-carbon.html )) - not just the intro but some of the links further down. A pity Crikey didn’t cover the recent conference, but Bernard Keane writes it off as “soil magic”.
I thought the idea was to arrest and reverse the anthropogenic factors driving global climate change.
Yes, we’ve cut down the trees and stripped the soils, among other things. Do you want to leave them like that?
I dunno, the NFF was pretty happy when Malcolm Turnbull pushed soil sequestration rewards into last year’s CPRS. Farmers resist if you just force them to dedicate part of their land to trees, but paying them to invest in higher future yields is another matter. In public investment terms it’s equivalent to fixing up the Murray-Darling basin or building bulk freight railway lines.
@tones9 … and a hundred year trend is a hundred year trend. I also spelled ‘kool-aid’ wrong so I guess you win.
Free Country – I was decidedly in another realm when I misinterpreted your claim that “I can’t even get anyone interested in the question of whether soil reconditioning with sequestered carbon could produce a climate-repair double dividend.” Clearly suffering a catatonic event, I assumed that you had discovered an innovative technology to gather up all the CO2 from industrial stacks and mining to sequester it in soil.
Projects to restore soil organic carbon (SOC) to agricultural lands is not new and there is some good work being performed. The NFF would be very pleased with carbon off-sets too particularly since the NFF are predominantly responsible for the loss of SOC to more than 75 percent of Australian farming soils.
One of Australia’s top soil experts, Dr Maarten Stapper, was dumped by the pro-GM CSIRO in 2007, amid allegations he was bullied by executive management for criticising genetically modified crops.
The chief of CSIRO’s Plant Industry division, Dr Jeremy Burdon, confirmed Dr Stapper had filed complaints alleging instances of bullying and harassment but these had been “appropriately dealt with and dismissed”. Dr Stapper was researching carbon loss in soils, restoring soil fertility by improving soil microbiology and use of biological farming.
CSIRO sources say Dr Stapper, was “carpeted” by management after he was overheard explaining criticisms of some aspects of GM crops while mingling with audience members after a public forum.
Meanwhile the donkeys strutting the halls of WA’s parliament, advise that Australia is a stringently regulated nation that guarantees against GM crop contamination. Buoyed by the green light, 300 farmers planted Monsanto’s Roundup ready (glyphosate) canola crops in WA last year.
Nearly 70% of an organic farmer’s property was contaminated and he has lost his accreditation. An outraged group of citizens are calling for donations from the public to bail the poor bugger out so if you have a few bob, send it his way. Monsanto has guaranteed to back the GM farmers in the event of litigation.
Sometime later, ten new populations of glyphosate resistant annual ryegrass were found in WA.The new populations resistance to the popular herbicide have almost doubled WA’s documented cases which are widespread.
“Scientists at the University of Adelaide’s Waite Research Institute have discovered new cases of herbicide resistance in annual ryegrass, the most serious and costly weed of Australian cropping.
“Paraquat is the only viable herbicide alternative to the most commonly used herbicide, glyphosate. With more than 100 annual ryegrass populations in Australia already having developed resistance to glyphosate, the discovery of paraquat resistance means that none of the currently available knockdown herbicides can be guaranteed to control ryegrass,” said Professor Christopher Preston.
Aw stuff it FC. Why should you or I care about SOC, rampant dryland salinity or the diabolical world of Monsanto?